5 December 2014

Physicists uncover new path to quantum computers

Researchers investigating a strange material show how it could advance the development of next-generation transistors for the superfast electronics of tomorrow.

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TALLAHASSEE, Fla. — A strange, iridescent material that has flummoxed physicists for 45 years turns out to be an exotic state of matter that could open a new path to quantum computers and other next-generation electronics.

Lu LiUniversity of Michigan physicist Lu Li at work in the MagLab's DC Field Facility.

Physicists working at the National High Magnetic Field Laboratory have discovered or confirmed several properties of the compound samarium hexaboride (SmB6) that raise hopes for finding the silicon of the quantum era. They say their results also close the decades-old case of how to classify the material.

Their research, "Two-dimensional Fermi surfaces in Kondo Insulator SmB6," has been published in the prestigious journal Science.

The researchers, from the University of Michigan, provide the first direct evidence that SmB6 is a topological insulator, an exciting class of solids that conduct electricity across their surface, but block it through their interior. Working in the lab's world-record 45 tesla hybrid magnet, the U-M team used a technique called torque magnetometry to observe tell-tale oscillations in the material's response to a high magnetic field that reveal how electric current moves through it.

"The 45 tesla hybrid magnet was essential to our project," said U-M physicist Lu Li, a co-author of the paper. "It helped us reach the quantum limit of the surface states of SmB6."

The team also showed that the surface of samarium hexaboride holds rare Dirac electrons, particles with the potential to help researchers overcome one of the biggest hurdles to quantum computing. This is particularly enticing to scientists because the electrons in SmB6 interact more closely with one another than those in most solids — making it what physicists call a strongly correlated material. This helps its interior maintain electricity-blocking behavior.

Samarium hexaborideSamarium hexaboride is a compound made of the metal samarium and the rare metalloid boron.

This deeper understanding of SmB6 raises the possibility that engineers might one day route the flow of electric current in quantum computers like they do on silicon in conventional electronics, said Li.

"Before this, no one had found Dirac electrons in a strongly correlated material," Li said. "We thought strong correlation would hurt them, but now we know it doesn't. While I don't think this material is the answer, now we know that this combination of properties is possible and we can look for other candidates."

Using particles like atoms or electrons to perform processing and memory tasks, quantum computers promise dramatic increases in computing power and security over today's machines.

Being part of the unraveling of the SmB6 mystery has been exciting, said DC Field Facility Director Tim Murphy, who oversees the magnets used in the research.

"SmB6 has resisted explanation for a number of years owing to the conflicting behaviors it displays at low temperatures," said Murphy. "The work by Lu Li and his group is fascinating because it utilizes recent theoretical work and cutting edge, high-field experimental results to explain the experimental enigma that has bedeviled scientists for many years."

The National High Magnetic Field Laboratory is the world’s largest and highest-powered magnet facility. Located at Florida State University, the University of Florida and Los Alamos National Laboratory, the interdisciplinary National MagLab hosts scientists from around the world to perform basic research in high magnetic fields, advancing our understanding of materials, energy and life. The lab is funded by the National Science Foundation (DMR-1157490) and the state of Florida. For more information, visit us online at nationalmaglab.org or follow us on Facebook, Twitter, Instagram and Pinterest at NationalMagLab.